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Constant Density (constant + density)
Selected AbstractsIs selection of host plants by Plagiodera versicolora based on plant-related performance?ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2008Sawako Egusa Abstract Plant-related performance may be one of the most important factors in the selection of host plants by insect herbivores. We investigated the importance of plant-related performance in host selection by the willow leaf beetle, Plagiodera versicolora (Laicharting) (Coleoptera: Chrysomelidae), on four willow species: Salix chaenomeloides Kimura, Salix eriocarpa Fr. et Sav., Salix integra Thunb., and Salix serissaefolia Kimura (Salicaceae). Bagging experiments in the field revealed that the performance of P. versicolora adults and larvae differed significantly among willow species under enemy-free conditions and at constant densities. Egg clutch and larval abundance were positively related to adult abundance. Plagiodera versicolora adults did not discriminate strongly among willow species for feeding and oviposition. Larval performance did not differ among willow species in the presence of natural enemies, suggesting that interspecific differences in host quality were overridden by mortality from natural enemies. Adult and egg clutch abundance of P. versicolora changed seasonally despite the temporal stability of adult and larval performance under enemy-free field conditions. Thus, plant-related performance of P. versicolora adults and larvae may contribute little to population growth and temporal dynamics of host use in P. versicolora. Potential factors that reduce discrimination of P. versicolora among host willow species are discussed. [source] Functional response and size-dependent foraging on aquatic and terrestrial prey by brown trout (Salmo trutta L.)ECOLOGY OF FRESHWATER FISH, Issue 2 2010P. Gustafsson Gustafsson P, Bergman E, Greenberg LA. Functional response and size-dependent foraging on aquatic and terrestrial prey by brown trout (Salmo trutta L.).Ecology of Freshwater Fish 2010: 19: 170,177. © 2010 John Wiley & Sons A/S Abstract ,, Terrestrial invertebrate subsidies are believed to be important energy sources for drift-feeding salmonids. Despite this, size-specific use of and efficiency in procuring this resource have not been studied to any great extent. Therefore, we measured the functional responses of three size classes of wild brown trout Salmo trutta (0+, 1+ and ,2+) when fed either benthic- (Gammarus sp.) or surface-drifting prey (Musca domestica) in laboratory experiments. To test for size-specific prey preferences, both benthic and surface prey were presented simultaneously by presenting the fish with a constant density of benthic prey and a variable density of surface prey. The results showed that the functional response of 0+ trout differed significantly from the larger size classes, with 0+ fish having the lowest capture rates. Capture rates did not differ significantly between prey types. In experiments when both prey items were presented simultaneously, capture rate differed significantly between size classes, with larger trout having higher capture rates than smaller trout. However, capture rates within each size class did not change with prey density or prey composition. The two-prey experiments also showed that 1+ trout ate significantly more surface-drifting prey than 0+ trout. In contrast, there was no difference between 0+ and ,2+ trout. Analyses of the vertical position of the fish in the water column corroborated size-specific foraging results: larger trout remained in the upper part of the water column between attacks on surface prey more often than smaller trout, which tended to seek refuge at the bottom between attacks. These size-specific differences in foraging and vertical position suggest that larger trout may be able to use surface-drifting prey to a greater extent than smaller conspecifics. [source] Large-scale topology optimization using preconditioned Krylov subspace methods with recyclingINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 12 2007Shun Wang Abstract The computational bottleneck of topology optimization is the solution of a large number of linear systems arising in the finite element analysis. We propose fast iterative solvers for large three-dimensional topology optimization problems to address this problem. Since the linear systems in the sequence of optimization steps change slowly from one step to the next, we can significantly reduce the number of iterations and the runtime of the linear solver by recycling selected search spaces from previous linear systems. In addition, we introduce a MINRES (minimum residual method) version with recycling (and a short-term recurrence) to make recycling more efficient for symmetric problems. Furthermore, we discuss preconditioning to ensure fast convergence. We show that a proper rescaling of the linear systems reduces the huge condition numbers that typically occur in topology optimization to roughly those arising for a problem with constant density. We demonstrate the effectiveness of our solvers by solving a topology optimization problem with more than a million unknowns on a fast PC. Copyright © 2006 John Wiley & Sons, Ltd. [source] Determination of the rate coefficients of the SO2 + O + M , SO3 + M reactionINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 3 2010S. M. Hwang Rate coefficients of the title reaction R31 (SO2 + O + M , SO3 + M) and R56 (SO2 + HO2, SO3 + OH), important in the conversion of S(IV) to S(VI), were obtained at T = 970,1150 K and ,ave = 16.2 ,mol cm,3 behind reflected shock waves by a perturbation method. Shock-heated H2/O2/Ar mixtures were perturbed by adding small amounts of SO2 (1%, 2%, and 3%) and the OH temporal profiles were then measured using laser absorption spectroscopy. Reaction rate coefficients were elucidated by matching the characteristic reaction times acquired from the individual experimental absorption profiles via simultaneous optimization of k31 and k56 values in the reaction modeling (for satisfactory matches to the observed characteristic times, it was necessary to take into account R56). In the experimental conditions of this study, R31 is in the low-pressure limit. The rate coefficient expressions fitted using the combined data of this study and the previous experimental results are k31,0/[Ar] = 2.9 × 1035 T,6.0 exp(,4780 K/T) + 6.1 × 1024 T,3.0 exp(,1980 K/T) cm6 mol,2 s,1 at T = 300,2500 K; k56 = 1.36 × 1011 exp(,3420 K/T) cm3 mol,1 s,1 at T = 970,1150 K. Computer simulations of typical aircraft engine environments, using the reaction mechanism with the above k31,0 and k56 expressions, gave the maximum S(IV) to S(VI) conversion yield of ca. 3.5% and 2.5% for the constant density and constant pressure flow condition, respectively. Moreover, maximum conversions occur at rather higher temperatures (,1200 K) than that where the maximum k31,0 value is located (,800 K). This is because the conversion yield is dependent upon not only the k31,0 and k56 values (production flux) but also the availability of H, O, and HO2 in the system (consumption flux). © 2010 Wiley Periodicals, Inc., Int J Chem Kinet 42: 168,180, 2010 [source] The constant-density region of the dark haloes of spiral galaxiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2001Paolo Salucci We determine a crucial feature of the dark halo density distribution from the fact that the luminous matter dominates the gravitational potential at about one disc scalelength Rd, but at the optical edge the dark matter has already become the main component of the galaxy density. From the kinematics of 137 spirals we find that the dark matter halo density profiles are self-similar at least out to Ropt and show core radii much larger than the corresponding disc scalelengths. The luminous regions of spirals consist of stellar discs embedded in dark haloes with roughly constant density. This invariant dark matter profile is very difficult to reconcile with the fundamental properties of the density distribution of cold dark matter haloes. With respect to previous work, the present evidence is obtained by means of a robust method and for a large and complete sample of normal spirals. [source] | ||||||||||